Fluoroprene copolymers



Unite States Patent FLUoRoPRaNE coPoLYMEns John M. Hoyt, Woodside, N.Y., assignor, by mesne assignments, to Minnesota Mining and hianufacturmg Company, St. Paul, Minn, a corporation of Deiaware NoDrawing. Application April 23, 1956 Serial No. 579,746

12 Claims. (Cl. 260-375) This invention relates to halogen-containingpolymeric compositions. In one aspect, the invention relates topolymeric fluoroprene compositions. More particularly in this aspect,the invention relates to elastomeric polymeric fluoroprene compositionsand the method for their manufacture.

-It is an object of this invention to provide new and useful polymericfluoroprene compositions having desirable chemical and physicalcharacteristics.

Another object of the invention is to provide new and useful polymericfluoroprene compositions, possessing elastomeric properties togetherwith good chemical and physical characteristics, and which can be easilyfabricated into a wide variety of useful articles of improved chemicaland physical stability.

Still another object of this invention is to provide new and usefulpolymeric fluoroprene compositions serving as protective coatings havingthe aforementioned characteristics and which can be readily applied tothe surfaces of a wide variety of useful articles.

Still another object of the invention resides in a process for obtainingthese polymeric compositions in good yields.

Various other objects and advantages inherent in the invention Willbecome apparent to those skilled in the art from the accompanyingdescription and disclosure.

It has now been found that the copolymerization of fiuoroprene and aperhalogenated ethylene having at least three fluorine atoms, such astrifluorochloroethylene or tetrafluoroethylene, under the conditionsmore fully hereinafter described, produces an elastomeric polymericfluoroprene composition possessing good chemical and physical stability,and resistance to oils, fuels and various strong chemical reagents.These polymeric products of fluoroprene with eithertrifluorochloroethylene or tetrafiuoroethylene constitute valuablemacromolecules and are adaptable to a wide variety of commercial uses.They possess low temperature flexibility in addition to t'heaforementioned properties of chemical and physical stability andresistance to oil and hydrocarbon fuels. They are also selectivelysoluble in various commercial solvents and serve as durable, flexible,protective coatings on surfaces which are subjected to environmentalconditions in which they may come into contact with any of theaforementioned corrosive substances.

In general, asmore fully hereinafter disclosed, the polymericcompositions of the present invention are produced from thepolymerization of monomeric mixtures containing .fiuoroprene witheithertrifluorochloroethylene or tetralluoroethylene as a comonomer, attemperatures between about -20 C. and about 150 C., with intermediatetemperature ranges being selected with reference to the specificpolymerization system employed. The most use- :ful elastomeric polymericcompositions of the present invention are copolymers produced frommonomeric mixtures containing between about mole percent and about 80mole percent fiuoroprene and the remaining major constituent beingeither trifluorochloroethylene or tetrafluo- "ice [ml roethylene. Thepreferred elastomeric copolymeric compositions of the present inventionare copolymers produced from monomeric mixtures containing between tabout 15 mole percent and about 80 mole percent fluoroprene and theremaining major constituent being either trifiuorochloroethylene ortetrafluoroethyiene.

In producing elastomeric copolymeric compositions from theaforementioned monomeric mixtures containing between about 5 molepercent and about mole percent fiuoroprene and the remaining majorconstituent being either of the aforementioned comonomers, it is foundthat the finished elastomeric product contains between about 50 molepercent and about mole percent fluoroprene and the remaining majorconstituent being either trifluorochloroethylene or tetrafluoroethylene.I11 producing elastomeric copolymeric compositions from theaforementioned monomeric mixtures containing between about 15 molepercent and about 80 mole percent fluoroprene and the remaining majorconstituent being either of the aforementioned comonomers, it is foundthat the finished elastomeric product contains between about 65 molepercent and about 95 mole percent fluoroprene and the remaining majorconstituent being either trifluorochloroethylene ortetrafiuoroe'thylene.

The criticality of the aforementioned monomeric feed ratios to producethe elastomeric fluoroprene copolymers of the present invention, willbecome apparent from the fact that although the high chemical andphysical stability and resistance to strong chemical reagents oftrifluorochloroethylene and te'trafluoroethylene is well-known,nevertheless, it is found that the fluoroprene content of thecopolyrneric compositions must be at least 50 mole percent in order toobtain a copolymericproduct that possesses the desired elasticity andextensibility in addition to the above-mentioned properties of physicaland chemical resistance to strong reagents.

The elastomeric polymeric compositions of the present invention arepreferably prepared by carrying out the polymerization reaction in thepresence of a free radical forming promoter. For this purpose, thepolymerization reaction is carried out by employing a water-solubleperoxy type initiator in a water-suspension type recipe or an organicperoxide initiator in a bulk-type system. The .W.ater-suspension typerecipe is preferred.

The water-suspension type system contains a watersoluble peroxy-typeinitiator, which is preferably present in the form of an inorganic,persulfate such as potassium persulfate, sodium persulfate or ammoniumpersulfate. In addition, the water-suspension type recipe system nayalsocontain, in some instances, a variable-valence metal salt, forexample, an iron ,salt such as ferrous sulfate or ferrous nitrate toaccelerate the copolymerization reaction. The water-soluble initiatorpresent in the watersuspension type recipe system comprises betweenabout 0:1 and about 5 parts by weight perlOO parts of total monomerspresent. The variable-valence metal salt is preferably employed in anamount between about 0.01 and about 0.2 .part by weight per parts oftotal monomers present. It is also desirable, in some instances, inthese water-suspension type recipe systems, that a reductant be present,preferably in the form of a bisulfite, such as sodium bisulfite,potassium bisulfite, sofdium metabisulfite or potassium .inetabisulfite.The reductant comprises between about 0.05 and about 5 parts by,weightper 100 parts of total monomers present; preferably the reductantcomprises between about 0.1 and about 2 parts by weight per 100 parts oftotal monomers present. i

In these water-suspension type recipesystems, 'it is desirable to employan emulsifying agent. This emulsifying agent is present either in theform of a, metallic salt sium stearate,

of an aliphatic acid having from 14 to 20 carbon atoms per molecule, orin the form of a halogenated-organic acid or salts thereof, having from6 to 18 carbon atoms per molecule. A typical example of the former ispotas- Typical examples of the halogenatedorganic acid or salts thereof,serving as emulsifying agents in the above-mentioned water suspensiontype recipe systems, are polyfluorocarboxylic acids (e. g.,perfluorooctanoic acid) or perfluorochlorocarboxylic acid salts (e. g.,trifiuorochloroethylene telomer acid soaps). The polyfluorocarboxylicacids which may be employed are such as those disclosed in U. S. PatentNo. 2,559,752; and the non-acidic derivative of the acids disclosedtherein as being effective dispersing agents may also be used in theprocess of the present invention. The perfluorochlorocarboxylic acidsalts which may be used in accordance with this invention are thosedisclosed in co-pending application Serial No. 501,782, filed April 18,1955, as

being useful dispersing agents in polymerization reactions. In general,these emulsifying agents are present in an amount between about 0.5 andabout 10 parts by weight per 100 parts of total monomers present.

The polymerization reaction is preferably conducted under alkalineconditions. It is desirable, therefore, that the pH be maintainedbetween about 7 and 11 in order to prevent gelling of the resultingpolymeric product, a condition which often causes slowdown or stoppageof the polymerization reaction. In this respect, it should be noted thatit is sometimes necessary to maintain the pH of the system within theaforementioned pH limits by the addition of suitable buffer agents.Typical examples are sodium borate and disodium phosphate.

As indicated above, the polymerization reaction may also be carried outwith the initiator being present in the form of an organic peroxide in abulk-type polymerization system. Of these organic peroxide promoters,halogen-substituted peroxides are most desirable. A preferred promoterof this type is trichloroacetyl peroxide. Other halogen-substitutedorganic peroxides for carrying out the polymerization reaction aretrifluorodichloropropionyl peroxide, trifluoroacetyl peroxide,difluoroacetyl peroxide, trichloroacetyl peroxide, 2,4-dichlorobenzoylperoxide and dichlorofluoroacetyl peroxide, benzoyl peroxide andditertiary butyl peroxide.

As previously indicated, the polymerization reaction is carried out, ingeneral, at a temperature between about C. and about 150 C. When thepolymerization reaction is carried out employing a water-suspension typerecipe, temperatures between about 5 C. and about 100 C. are preferablyemployed. When the polymerization reaction is carried out in thepresence of an organic peroxide initiator in a bulk-type polymerizationsystem, temperatures over the entire range of between about 20 C. andabout 150 C. are preferably employed depending upon the decompositiontemperature of the promoter. The polymerization reactions describedherein to produce the polymeric compositions of the present inventionare carried out under autogenous conditions of pressure.

As previously indicated, the polymeric compositions of the presentinvention are particularly suitable and useful when employed in the formof durable, flexible coatings on a Wide variety of surfaces, andparticularly on surfaces which are subjected to distortion in normaluse, such as fabric surfaces. For this purpose, the polymericcomposition may be dissolved in various commercial solvents.Particularly useful solvents comprise the aliphatic and aromatic esters,ketones and halogenated hydrocarbons. Typical examples of these solventsare di-isobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone,ethyl acetate and 1,l,Z-trifluorotrichloroethane. In this respect, itshould be noted that it is often desirable to regulate the molecularWeight of the polymeric compositions of the present invention in orderto obtain greater solubility in organic solvents. It is found that theaddition of various polymerization modifiers appreciably reduces themolecular weight of the polymeric compositions and increases theirsolubility, without affecting, unduly, the overall yield. Suitablepolymerization modifiers include chloroform (CHCl Freon-113 (CF ClCFClcarbon tetrachloride (CCl trichloroacetyl chloride (CCl COCl),bromotrichloromethane (CBrCl dodecyl mercaptan (C H SH) and mixedtertiary mercaptans. These modifiers are preferably added in amountsbetween about 0.01 and about 10 parts by weight per parts of totalmonomers charged to the polymerization reaction. Dodecyl marcaptan ispreferred.

The following examples are offered for a better understanding inproducing the elastomeric copolymeric compositions of the presentinvention and are not to be construed as limiting its scope.

Example I A heavy-walled glass polymerization tube of about 20 ml.capacity was flushed with nitrogen and then charged with 9 ml. of asolution which had been prepared by dissolving 25 grams of potassiumstearate in 900 ml. of water, adjusting this solution to a pH of 10.2,and thereafter adding 1.5 grams of dodecyl mercaptan. The 9 ml. of thesoap-mercaptan solution in the polymerization tube was then frozen, andthe tube was then charged with 1 ml. of a promoter solution, prepared bydissolving 1.5 grams of potassium persulfate in 100 ml. of water. Thecontents of the tube were then refrozen, and the tube was next connectedto a gas-transfer system and evacuated at liquid nitrogen temperature.To the frozen contents of the tube were added, by distillation, 1.91grams of fiuoroprene and 3.09 grams of trifluorochloroethylene, whichcomprised a 1:1 mole ratio. After the contents of the tube werethoroughly frozen with liquid nitrogen, the tube was evacuated andsealed.

The polymerization tube and contents were agitated in atemperature-regulated water-bath at 50 C. for a period of 73 hours. Atthe end of this time, the contents of the tube were coagulated byfreezing. The coagulated product was then removed from the tube, washedwith hot water and then dried to constant weight in vacuo at 35 C. Acopolymeric rubbery product was obtained which was found, upon analysis,to comprise 78 mole percent fluoroprene, and the remaining majorconstituent, trifluorochloroethylene, being present in an amount ofapproximately 22 mole percent. The copolymer was obtained in an amountcorresponding to an 18 percent conversion.

Example 11 Employing the procedure set forth in Example I and the samepolymerization system, the tube was charged with 2.09 grams offiuoroprene and 2.90 grams of tetrafluoroethylene, which comprised acomonomer mixture containing 50 mole percent fiuoroprene and 50 molepercent tetrafluoroethylene. The polymerization reaction was carried outat a temperature of 50 C. for a period of 96 hours. The resultantelastomeric product was worked-up in accordance with the same procedureas set forth in Example I. A rubbery product was obtained and, uponanalysis, was found to comprise approximately 78 mole percentfiuoroprene, and the remainingmajor constituent, tetrafluoroethylene,being present in an amount of approximately 22 mole percent. Thecopolymer was obtained in an amount corresponding to a 30 percentconversion.

Example III frozen contents of the tube were then charged 4 ml. of

a solution of potassium persulfate, prepared by dissolving 1 gram ofpotassium persnlfate in 80 ml. of water.

Thereafter, 1 ml. of a solution of sodium metabisulfite was added, whichhad been prepared by dissolving 0.4 gram of sodium rnetabisulfite in 20ml. of water. Thereafter, the contents of the tube were refrozen inliquid nitrogen. The tube was then connected to a gas-transfer systemand evacuated at liquid nitrogen temperature.

To the frozen contents of the tube were added, by distillation, 1.25grams of fiuoroprene and 3.75 grams of trifluorochloroethylene, whichcomprised a comonomer mixture containing 35 mole percent fiuoroprene and65 mole percent trifluorochloroethylene.

The polymerization tube was then sealed under vacuum and agitated in atemperature-regulated water-bath at 50 C. for a period of 24 hours. Atthe end of this time, the contents of the tube were coagulated byfreezing. The coagulated product was then removed from the tube, washedwith hot water and then dried to constant weight in vacuo at 35 C. Acopolymeric elastomeric product was obtained which was found, uponanalysis, to comprise 80.5 mole percent fiuoroprene, and the remainingmajor constituent, trifiuorochloroethylene, being present in an amountof approximately 19.5 mole percent. The copolymer was obtained in anamount corresponding to a 20 percent conversion.

A sample of the raw copolymer was compression molded at 250 -F.for aperiod of approximately minutes. After molding, the sample retained itsrubbery characteristics. Gehman stiffness of the molded sample of rawcopolymer determined according to ASTM Designation, D105349T, was asfollows:

Example IV Employing the procedure set forth in Example III and the samepolymerization system, the tube was charged with 3.25 grams offiuoroprene and 1.75 grams of trifiuorochloroethylene, which comprised acomonomer mixture containing 75 mole percent fiuoroprene and 25 molepercent trifluorochloroethylene. The copolymerization reaction wascarried out at a temperature of 50 C. for

,a period of 25 hours. The resultant elastomeric product was worked-upin accordance with the same procedure as set forth in Example III. Arubbery product was obtained and, upon analysis, Was found to compriseapproximately 93 mole percent fiuoroprene, and the remaining majorconstituent, trifluorochloroethylene, being present in an amountofapproximately 7 mole percent. The

copolymer was obtained in anamount corresponding to a 40percentconversion.

A sample of the raw copolymer was compression Example V Employing theprocedure set forth in Example III and the same polymerization system,the tube was charged with 1.46 grams of fiuoroprene and 3.54 grams oftrifiuoroehloroethylene, which comprises a comonomer mixture containing40 mole percent fiuoroprene and 60 mole percent trifluorochloroethylene.The polymerization reaction was carried out at a temperature of 50 C.for

use.

a period of 24 hours. The resultant elastomeric product was worked-up inaccordance with the same procedure as set forth in Example III. Arubbery product was obtained and, upon analysis, was found to compriseapproximately 82 mole percent fiuoroprene, and the remaining majorconstituent, trifluorochloroethylene, being present in an amount ofapproximately 18 mole percent. The copolymer was obtained in an amountcorresponding to a 28 percent conversion.

A sample of the raw copolymer was compression molded at 250 F. and for aperiod of approximately 10 minutes. After molding,.the sample retainedits rubbery characteristics. A volume increase of 92.7% was observed inthe molded sample, when tested by ASTM Designation, D471-49T, in ASTMType II Fuel, described above.

Example VI roprene, and the remaining major constituent, tetrafluo-.roethylene, being present in an amount of approximately 9.5 molepercent. The copolymer was obtained in an amount corresponding to a 50percent conversion.

As previously indicated, the polymeric compositions of the presentinvention possess highly desirable physical and chemical propertieswhich make them useful for fabrication of a wide variety ofthermoplastic articles,

or for the application to various surfaces as protective coatings. Insuch uses, a raw elastomeric copolymer,

such as is produced in accordance with the procedure set forth in theabove examples, is extruded or pressed into sheets at temperaturesbetween about 250 F. and about 400 F. and at a pressure between about500 and about 15,000 pounds per square inch for a period of about 5 toabout 60 minutes. Thereafter, various articles can be molded frompreforms cut from sheets and extruded stock in the form of gaskets,diaphragms, packings, etc. In this respect, it is preferred in suchapplications, that the rawcopolymer also includes various vulcanizingagents and fillers.

When employed as protective coatings on any of the surfaces previouslydescribed, the raw copolymeric composition is dissolved in any of theaforementioned solvents and is applied to the desired surfaces,employing such apparatus as a knife-spreader or a doctor-blade or areverse-roll coater. The solvent, after the copolymeric coatingcomposition has been applied to the surface, is permitted to evaporate.This may also be accomplished in the presence of elevated temperatures,if so desired. In many applications, it is desirable to include in thecopolymeric coating composition, various vulcanizing agents. In thelatter case, supplementary heat-treatment of the coating is required,either during the solventremoval step or thereafter. After the solventhas been completely evaporated, the coated surface is ready for In thisrespect, it should be noted that the polymeric coating composition maybe applied to the surface either as a single coating or, if so desired,the protective coating may be built-up by the application of severallayers, each layer being permitted to harden by solvent evaporationbefore the next layer is applied. Furthermore, if so desired, theprotective coatings, or the polymeric composition, when obtained in theform of sheets, may be suitably pigmented.

Other uses for the polymeric compositions of the present inventionreside in the fabrication of belting,

hose, mountings, piston and pump-valves, sheet and valvedisks, rolls,tubing, pressure-sensitive tape for electrical insulation purposes,grommets, or as adhesives for fastening a rubber surface to a metal oranother rubber surface.

Since certain changes may be made in carrying out the process of thepresent invention in producing the desired polymeric compositionswithout departing from the scope of the invention, it is intended thatall matter contained in the above description is to be interpreted asillustrative and not in a limiting sense.

I claim:

1. A process for producing an elastomeric polymer which comprisespolymerizing a monomeric mixture of fluoroprene and a perhalogenatedethylene selected from the group consisting of trifiuorochloroethyleneand tetrafluoroethylene, said mixture containing between about molepercent and about 80 mole percent fluoroprene and the remaining majorconstituent consisting essentially of the perhalogenated ethylene, inthe presence of a free radical forming polymerization promoter at atemperature between about 20 C. and about 150 C.

2. A process for producing an elastomeric polymer which comprisespolymerizing a monomeric mixture of fluoroprene and a perhalogenatedethylene selected from the group consisting of trifluorochloroethyleneand tetrafluoroethylene, said mixture containing between about molepercent and about 80 mole percent fluoroprene and the remaining majorconstituent consisting essentially of the perhalogenated ethylene, inthe presence of a free radical forming polymerization promoter at atemperature between C. and about 150 C.

3. A process for producing an elastomeric polymer which comprisespolymerizing a monomeric mixture of fluoroprene andtrifluorochloroethylene, said mixture containing between about 5 molepercent and about 80 mole percent fluoroprene and the remaining majorconstituent consisting essentially of trifluorochloroethylene, in thepresence of a free radical forming polymerization promoter at atemperature between about 20 C. and about 150 C.

4. A process for producing an elastomeric polymer which comprisespolymerizing a monomeric mixture of fluoroprene andtrifluorochloroethylene, said mixture containing between about 15 molepercent and about 80 percent fluoroprene and the remaining majorconstituent consisting essentially of trifiuorochloroethylene, in thepresence of a free radical forming polymerization promoter at atemperature between about 20 C. and about 150 C.

5. A process for producing an elastomeric polymer which comprisespolymerizing a monomeric mixture of fluoroprene and tetrafluoroethylene,said mixture containing between about 5 mole percent and about 80 molepercent fluoroprene and the remaining major constituent consistingessentially of. tetrafluoroethylene, in the presence of a free radicalforming polymerization promoter at a temperature between about 20 C. andabout 150 C.

6. A process for producing an elastomeric polymer which comprisespolymerizing a monomeric mixture of fluoroprene and tetrafluoroethylene,said mixture con taining between about 15 mole percent and about 80 molepercent fluoroprene and the remaining major constituent consistingessentially of tetrafluoroethylene, in the presenceof a free radicalforming polymerization promoter at a temperature between about 20 C. andabout 150 C.

7. An elastomeric copolymer of about mole percent to about 95 molepercent fluoroprene and correspondingly about 50 mole percent to about 5mole percent of a perhalogenated ethylene selected from the groupconsisting of trifiuorochloroethylene and tetrafluoroethylene.

8. An elastomeric copolymer of about mole percent to about mole percentfluoroprene and correspondingly about 35 mole percent to about 5 molepercent of a perhalogenated ethylene selected from the group consistingof trifluorochloroethylene and tetrafluoroethylene.

9. An elastomeric copolymer of about 50 mole percent to about 95 molepercent fluoroprene and correspondingly about 50 mole percent to about 5mole percent trifluorochloroethylene.

10. An elastomeric copolymer of about 65 mole percent to about 95 molepercent fluoroprene and correspondingly about 35 mole percent to about 5mole percent trifluorochloroethylene.

11. An elastomeric copolymer of about 50 mole percent to about 95 molepercent fluoroprene and correspondingly about 50 mole percent to about 5mole percent tetrafluoroethylene.

12. An elastomeric copolymer of about 65 mole percent toabout 95 molepercent fluoroprene and correspondingly about 35 mole'percent to about 5mole percent tetrafluoroethylene.

References Cited in the file of this patent UNITED STATES PATENTS2,462,347 Barrick Feb. 22, 1949 2,468,664 Hanford Apr. 26, 19492,479,367 Joyce Aug. 16, 1949 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No, 2,843,575 T July 15, 1958 John Mu Hoyt It ishereby certified that error appears in the printed specification of theabove numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column '7, line 4'7 for "80 percent" reed m 89 mole percent Signed andsealedv this 18th day of November 1958,

(SEAL) Attest:

KARL Ho AXLINE ROBERT c. WATSON Attesting Officer Commissioner ofPatents

1. A PROCESS FOR PRODUCING AN ELASTOMERIC POLYMER WHICH COMPRISESPOLYMERIZING A MONOMERIC MIXTURE OF FLUOROPRENE AND A PERHALOGENATEDETHYLENE SELECTED FROM THE GROUP CONSISTING OF TRIFLUOROCHLOROETHYLENEAND TETRAFLUOROETHYLENE, SAID MIXTURE CONTAINING BETWEEN ABOUT 5 MOLEPERCENT AND ABOUT 80 MOLE PERCENT FLUOROPRENE AND THE REMAINING MAJORCONSTITUENT CONSISTING ESSENTIALLY OF THE PERHALOGENATED ETHYLENE, INTHE PRESENCE OF A FREE RADICAL FORMING POLYMERIZATION PROMOTER AT ATEMPERATURE BETWEEN ABOUT -20*C. AND ABOUT 150*C.
 7. AN ELASTOMERICCOPOLYMER OF ABOUT 50 MOLE PERCENT TO ABOUT 95 MOLE PERCENT FLUOROPRENEAND CORRESPONDINGLY ABOUT 50 MOLE PERCENT TO ABOUT 5 MOLE PERCENT OF APERHALOGENATED ETHYLENE SELECTED FROM THE GROUP CONSISTING OFTRIFLUOROCHLOROETHYLENE AND TETRAFLUOROETHYLENE.